While mathematically, F-theory describes a spacetime with an additional time direction, physically it's simply a convenient geometry in terms of which to understand a certain aspect of the type IIB theory in the usual (9+1) spacetime dimensions.

While mathematically, F-theory describes a spacetime with an additional time direction, physically it's simply a convenient geometry in terms of which to understand a certain aspect of the type IIB theory in the usual (9+1) spacetime dimensions.

But what exactly is this extra time direction, and what makes it seem possible?

To my understanding, super symmetry only works in 11 or less dimensions is you're working with 1 time dimension and the rest spacial. Beyond that you get particles of spin greater than 2 and they have problems.

You can, however, remove these problems in 12 dimensions if you have 2 time dimensions, in that your metric signature would be (-,-,+,...,+) (or whatever your preference for writing the signature signs is ;)). It's much less of a physical situation, more of a mathematical tool to conveniently talk about some things in IIB theory (it's SL(2,Z) symmetry I think).